1. Field of the Invention
The present invention relates to an RFID system, a reader-writer, and an RFID tag.
2. Description of the Related Art
In recent years, RFID (Radio Frequency IDentification) tags having predetermined identification information given thereto were widely used and RFID systems for managing production, physical distribution, products, and the like were suggested. The RFID system includes RFID tags attached to plural products and a reader-writer, reading the identification information of the RFID tags (for example, see Patent Document 1).
Patent Document 1: JP-A-2006-238381
In known RFID systems, when the reader-writer transmits a reading command, plural unspecified RFID tags existing in a range where RF waves arrive respond at a time. Accordingly, when response signals in the same RF band from the plural RFID tags collide with each other, or the like, only the response signal having the highest signal level was read and thus it was difficult to read all the RFID tags. Therefore, when the reading could not be made at a predetermined time to read, there is a problem that a non-read RFID tag which is permanently not detected remains.